Field of the Invention
The present invention relates to decreasing the amount of diluent needed to convert a heavy oil to a bitumen product that can be transported by pipeline. More specifically, the invention relates to a method and apparatus for partially upgrading heavy oil into a lower viscosity bitumen product. The invention provides a method to produce superheated steam at 1000-2200° C. at high velocity and use it to entrain and atomize heavy oil, where the high temperatures initiate oil upgrading reactions that crack heavier hydrocarbons to lighter ones reducing the amount of diluent needed to transport the oil in a pipeline and increasing its value.
Description of Related Art
Canadian oil sands bitumen produced with the Steam Assisted Gravity Drainage (SAGD) method is a heavy high viscosity product. The heavy oil is typically blended with a diluent at the production site to reduce its viscosity and make it amenable to pipeline transport. Diluent can be from naphtha, natural gas liquids (NGL) or upgraded bitumen (synbit). Naphtha and NGL are the preferred options because it takes lower amounts of these diluents (about 30%) than synbit (about 50%). However, this need for diluent adds a $10-15/bbl cost for the bitumen producer.
Heavy oil, also referred to as bitumen, typically has an American Petroleum Institute (API) gravity in the range of 8°-12°, and is immobile at ambient temperatures. This bitumen is produced from oil formations by two methods a) surface mining and b) in-situ thermal production (i.e., SAGD). The produced oil is either upgraded to a bottomless synthetic crude oil (SCO) or blended with light diluent for transport in conventional pipelines. Most heavy oil upgrading processes aim to upgrade the oil to a final sellable product and are very capital intensive. The process for upgrading bitumen typically includes carbon rejection technologies such as coking or visbraking followed by hydrotreating of the cracked product to convert unsaturated hydrocarbons to saturated ones. Many variations of this basic process design have been proposed. Fluid coking, flexicoking and hydrocracking have also been proposed for upgrading projects.
Upgrading is usually associated with mined bitumen projects in Canadian tar-sands oil recovery. SAGD bitumen which is lighter is typically not field upgraded but is instead blended with a light diluent for pipeline transport to refineries for processing. The blended bitumen and diluent oil is referred as dilbit. Dilbit needs to have a viscosity of 350 cSt and a density of 940 kg/m3 to meet typical pipeline transport requirements. The diluent presents an operating cost to the SAGD producers as its value is not recovered completely. Partial upgrading reduces bitumen viscosity and density to meet pipeline specification thus reducing or eliminating the need for diluent which will reduce operating cost and increase pipeline capacity. This type of upgrading for diluent reduction minimizes carbon rejection and gas formation aiming instead to preserve the oil volume. In the literature the terms “upgrading” and “partial upgrading” are used interchangeably but as utilized herein, the term “partial upgrading” is employed to describe processes that do not include significant carbon rejection in the form of coke but aim instead to reduce the diluent needed for transporting bitumen to market.
Several partial upgrading for diluent reduction technologies have been proposed in the literature. For instance, U.S. Pat. No. 6,852,215 B2 to Wen et al describes a partial upgrading process where the heavy oil is contacted by a hot syngas consisting primarily of H2, CO and N2. The syngas is produced preferably by the partial oxidation of natural gas and air but other fuels can be used as well. The syngas temperature is 650-1650° C. The heat from the syngas production is used to vaporize a portion of the heavy oil which allows upgrading reactions to proceed. The hydrogen in the syngas reacts with upgraded oil to minimize formation of unsaturated hydrocarbons. Further evaporation of unupgraded oil quenches the upgrading reactions and prevents generation of unwanted waste materials.
U.S. Pat. No. 6,989,091 B2 to Jorgensen describes an upgrading process where a heavy oil, preheated to just below the temperature where upgrading reactions start, is contacted with a hot gas jet to initiate upgrading reactions and the resulting load is injected into a non-catalytic reactor that is at a higher temperature (430-480° C.) than the initial oil temperature. The gas is preferably steam at a temperature of 600 to 800° C.
U.S. Pat. No. 7,947,165 B2 to Berkowitz et al discloses the use of supercritical water as a means to upgrade heavy oil. The process requires very high pressures (34-135 bar) at operating temperatures of 250-450° C. It also describes residence times up to 1 minute. These conditions lead to decreases in saturated hydrocarbon content and increases in aromatic content which degrade the quality and value of the oil.
U.S. Pat. No. 7,229,483 B2 to Lewis describes a gasification method based on an ultra-superheated steam. The formation of superheated steam is accomplished with a burner operating with a fuel like natural gas and a mixture of steam and oxygen. The stoichiometric ratio of fuel to oxygen is near the required ratio for complete combustion of fuel and oxygen to carbon dioxide and water. The mixture of steam and oxygen is referred to as artificial air as it has an oxygen concentration similar to that of atmospheric air. This method has some drawbacks as the need to premix and preheat oxygen and steam and the low oxygen concentration in steam which increases the length and dimensions of the combustion chamber compared to oxyfuel combustion.
In addition, certain type of thermal nozzles, have been described in the related art, primarily directed to combustion applications rather than oil upgrading. For instance, U.S. Pat. No. 5,266,024 to Anderson described a method for providing an oxidant employing a thermal nozzle to convert thermal energy to kinetic energy. The method describes the production of a high velocity and high temperature oxygen stream that can be used to supply an oxidant to a combustion zone. The method applies to combustion applications.
U.S. Pat. No. 6,450,108 B1 to Bool III, et al describes a device that is employed to combust a difficult to combust liquid by using the high velocity oxidant jet to atomize the liquid and improve the contact of the fuel contained in the liquid and oxygen to provide a high temperature environment that ignites and sustains combustion of the liquid.
U.S. Pat. No. 6,565,010 B2 to Anderson et al describes an efficient liquid atomizer using a hot gas accelerated to high velocity. The particular invention demonstrates how by using this atomizer very small droplets can be produced even with very viscous fluids.
The related art discussed above does not address the need to decrease the amount of diluent required to convert heavy oil, such as SAGD bitumen, to a product that can be transported by pipeline. An object of the current invention is to minimize the diluent usage and production of low value by-products such as gas and coke. Another object of the invention is to provide a thermally integrated method and apparatus for partially upgrading a heavy oil in the form of a hydrocarbon emulsion or dilbit where superheated steam at 1000-2000° C. and high velocity is utilized to entrain and atomize the heavy oil.
One of the advantages associated with the present invention is the high temperature initiates oil upgrading reactions by cracking heavier hydrocarbons to lighter ones.
Other objects and aspects of the present invention will become apparent to one of ordinary skill in the art upon review of the specification, drawings and claims appended hereto.